Question

In backbone.js, I want to do:

initialize: =>
  @collection.on("add", @appendModel(model)) # <- how to correctly write it?

render: =>
  # do some render
  @collection.each(@appendModel())

appendModel: (model) ->
  # append model to $el

Currently, i have @collection.on("add", @render), but that redraws the whole collection. I want to just fire appendModel(), but I’m not sure how to pass the model in the argument in this case.

Answer 1

In your example you are first invoking the @appendModel method with an argument model, and then passing the return value to collection.on:

@collection.on("add", @appendModel(model))

You need to pass a reference to the method instead:

@collection.on("add", @appendModel)

The caller (in this case Backbone) will pass the argument to the method for you.

You might also need to pass this (or @) as a third argument to the collection.on method. This is the context argument which tells Backbone that when the callback is executed, the this context should be set tot that value:

@collection.on("add", @appendModel, @)

Or because you’re using coffeescript, you can just skip that bit and define the @appendModel method with the fat arrow notation, which will ensure that the this context is bound to your view:

appendModel: (model) =>